Ethanol is an important fuel. In general, ethanol can be produced from cellulose in a two step process, sometimes referred to as biomass conversion. The first step hydrolyzes cellulose to sugar. The sugar is then fermented in the second step to form ethanol. The method and apparatus of this specification relates to the first step—the hydrolysis of cellulose. More specifically, the method and apparatus relates to splitting the outer husk of cellulose material. The split, outer husk is then further refined in successive stages, whereby the combination of stages converts the cellulose to sugar.
The fermentation of the sugar to ethanol is well understood. Hydrolysis of the cellulose is, however, the Achilles heel in the process of making ethanol. To achieve overall profitability from ethanol production the ratio of the energy content of the ethanol to the energy used for producing the ethanol must be high. Many approaches have been used to accomplish this level of efficient production of ethanol. However, the production of ethanol continues to be highly subsidized indicating that it has not yet achieved a high level of profitability. There are many factors contributing to this. One factor is the use of high value, high cost feedstock such as corn, which has high level of available sugar. Another is the cost of transportation of the feedstock to an ethanol production plant that is remote from the feedstock production site.
Corn and other high value sources of cellulose are used due to the difficulty of converting other sources of cellulose such as wood, wood chips, saw dust, lumber, newspaper, cardboard, sugar cane, and ground straw into sugar. The other sources of cellulose have a relatively low level of available sugar. These sources contain not only cellulose, but also lignin and hemi-cellulose which must be separated from the cellulose before sugar is available for fermentation. The method and apparatus disclosed in this specification efficiently carries out the first task of splitting the raw cellulose so further refining in subsequent stages results in a high sugar yield at a low energy cost with greater profitability than the methods and apparatus available today.
Transportation of the raw cellulose bearing material from its geographical source to the location of an ethanol production plant is costly. The ethanol production process could be made more profitable if the production of sugar from cellulose was located at the source of the cellulose. Cellulose could be granulated and converted on site to sugar. The unwanted by-products from conversion, which may represent up to 50% of the weight of the unprocessed cellulose, could also be disposed of on site. The cost of shipping to a distant ethanol production plant for fermentation to ethanol would thereby be significantly reduced.
Alternatively, the entire ethanol plant could be sited at a large, long term source of cellulose and the resultant ethanol piped to users.
But regardless of what approach is taken, the reactor pump efficiently carries out its task of splitting the cellulose husks. And it is compact, scalable, and meets the needs of the conventional ethanol plant or a plant located at the source of the cellulose.